6 
BULLETIN 1450, U. S. DEPARTMENT OF AGRICULTURE 
ogists in regard to the homology of the mesocotyl and of the coleo- 
phyll of grasses. The mesocotyl has been regarded both as an in- 
ternode and as an elongated node. The coleophyll has been desig- 
nated by some botanists as the cotyledon, by others as the enlarged 
ligule of the cotyledon, and again by others as an ordinary leaf in 
which the sheath only is represented (&£, p. 7-26; 12, vol. 2, p. bH- 
416; 19, p. 165-174; 7, p. 175-183; 39, p. 179-182). 
On one timothy seedling examined which did not grow through 
the surface of the soil a lower internode of the shoot was slightly 
elongated, and there was a nodal root 0.4 of an inch above the whorl 
of roots at the tip of the mesocotyl. This type of elongation is rare 
in timothy seedlings. It is similar to the elongation of underground 
rooting stems observed on older timothy plants which have been 
covered with soil (37, p. 173-178). 
RELATION OF DEPTH OF SOWING TO GROWTH OF MESOCOTYL AND COLEOPHYLL 
In order to determine the effect of depth of sowing upon the 
development of the mesocotyl and of the coleophyll, seeds of ordinary 
timothy were sown in a greenhouse at different depths on December 
23, 1920. Fifty seeds were sown in each of duplicate pots at each 
depth. The soil, which was a loam, was kept continually moist. 
The temperature in the greenhouse ranged from 48° to 60° F. Con- 
ditions Avere very favorable for germination and growth. 
Dry soil was first firmly compacted in the pots up to the level at 
which the seeds were sown. In two of the pots the seeds were sown 
approximately at the surface, enough soil being scattered over them 
to cover them partially. In the other pots enough soil was placed 
over the seeds so that they were at approximately the depths indi- 
cated in Table 2. 
Table 2. — Percentage of timothy seeds sown at different depths which had 
produced growth above the surface of the soil on different days after the 
seeds were sown 
Depth sown 
Number of days after sowing 
8 
11 
13 
15 
18 
22 
29 
34 
Per cent 
17 





Per cent 
41 
21 
3 



Per cent 
53 
43 
19 



Per cent 
55 
46 
30 
1 


Per cent 
57 
48 
34 
2 


Per cent 
57 
48 
34 
4 


Per cent 
57 
48 
34 
5 


Per cent 
57 
0.5 inch deep. 
48 
34 
5 

2.5 inches deep. 

The data in Table 2 show that the percentage of seedlings which 
developed was largest from seeds sown at the surface and that this 
percentage decreased as the depth of sowing increased. Relatively 
few seedlings grew from seeds 1.5 inches below the surface and none 
from seeds 2 or 2.5 inches deep. Although large numbers of the 
seeds sown at these depths germinated, they did not produce growth 
above the surface of the soil. 
A series of measurements was made of the timothy seedlings re- 
ferred to in the preceding paragraphs and of some others growing 
